Golf putter heads have long been made from wood and metal. More recent efforts involve combining various materials.
Current theory in golf putter head design teaches that it is preferable to have a relatively large portion of the club face composed of material of a relatively low specific gravity. This gives the putter head a larger "sweet spot", which is generally understood as the area of the club face which can contact the golf ball, and still provide a true, accurate and desired trajectory of the golf ball. The larger the sweet spot, generally the more forgiving the club head is. That is, a larger sweet spot will permit satisfactory contact with the ball using a less perfect swing. A larger sweet spot generally improves the scores of most golfers.
It also is necessary to provide the putter head with a certain mass, generally in the range of 300 to 325 grams, to allow the transfer of sufficient momentum to the golf ball during putting. A variety of devices have been employed, including perimeter, bottom and heel and toe weighting, to concentrate the mass and thereby enlarge the sweet spot on the face of the putter. Other devices have used other materials as inserts or striking surface covers in attempts to concentrate the mass and enlarge the sweet spot.
Putter performance also is enhanced by a softer putting face. Conventional metal putters are relatively hard. While recent improvements, including inserts of softer materials on the putter face, yield better results, softer striking faces could further improve putter heads. Additionally, current devices and methods which modify softness require significant changes in weighting materials, thereby precluding relatively efficient and economic production of a range of putter heads of different softness.
Unlike golf clubs other than putters, which must withstand much greater forces of impact from the golf ball due to the harder swings, putters can be of much lower tensile strength and hardness than non-putter golf clubs.
Marketability of putter heads is enhanced if the putter can be colored in an economic and relatively permanent manner. Some golfers desire colorful putters. Current putter heads cannot be colored economically and relatively permanently. Paints and other coloring coatings scratch easily and are otherwise not very durable.
No currently marketed device is known to this applicant that employs a polyurethane body with concentrated weighting, to maximize the sweet spot, lower surface softness while maintaining acceptable club weight, and permitting color and softness variations without significant additional manufacturing expense.